Re: [Qemu-devel] Re: [PATCH] megasas: LSI MegaRAID SAS HBA emulation

[Gerd Hoffmann]

On 11/17/09 11:51, Hannes Reinecke wrote:
> Grand. Meanwhile I've dug up some more register definitions,
> so I'll doing some more updates to the driver.

Feel free to send updates (both incremental and replacement are fine).

> Meanwhile I've stumbled across another issue:
> The megasas HBA insists on returning some data like inquiry
> or VPD pages during init/configuration.
>
> I can't really use the normal command completion here,
> as eg on megasas configuration command requires me
> to issue several requests to the underlying device.

Well, you can, but it probably isn't very convenient ...

Easy way out would be calling qemu_aio_wait(), when it returns you can 
be sure the request is finished (and the completion callback was 
called).  You probably have to flag the request as being special 
somewhere in req->hba_private so your completion callback will not apply 
the usual processing.

Calling qemu_aio_wait() is only needed if there is actually something in 
flight asynchronously.  req->status is initialized to -1 and set to a 
status code on completion, so you can use that to figure whenever the 
request is still being processed.  All commands emulated by scsi-disk 
will complete instantly, i.e. the completion callback will be called 
before scsi_req_{buf,sgl} returns.  Only with scsi-generic you'll find 
INQUIRY being processed really asynchronously.

cheers,
  Gerd